The Domain Name System (DNS) is a hierarchical distributed naming system for computers, services, or any resource connected to the Internet or a private network. It associates various information with domain names assigned to each of the participating entities. DNS also translates more readily memorized domain names to the numerical Internet Protocol (IP) addresses used to locate and identify computer services and devices with the underlying network protocols.
Authoritative DNS servers, also known as authoritative name servers or authoritatives, respond to queries about the mapping of domain names to numerical IP addresses and also to requests for other resource records (RRs), such as mail exchanger (MX) records. To respond to these queries, each authoritative has its own DNS database of DNS records. Common types of records stored in a DNS database include IP addresses (A and AAAA), Simple Mail Transfer Protocol (SMTP) MX records, and name server (NS) records for the corresponding domain. A DNS database can also store records for other types of data, including domain name aliases (CNAME) and DNS Security Extension (DNSSEC) records, which can be used to authenticate DNS records.
To add a new domain to the Internet, basic DNS standards call for the domain owner, or registrant, to purchase a domain name from a registrar and specify the names of the authoritative DNS servers used to answer queries for the new domain. The registrant obtains authoritative DNS service from an authoritative DNS provider (such as Dynamic Network Services Inc. of Manchester, N.H.) and configures the records for its domain name (or more precisely, zone) with the authoritative DNS provider. When an end user's machine attempts to access the new domain name, it asks a recursive DNS server to retrieve a DNS record for the new domain, most commonly an A or AAAA (IPv4 or IPv6 address). The recursive server locates the authoritative DNS server maintained by the authoritative DNS provider, then queries the authoritative DNS server for the DNS record. The recursive DNS server returns the authoritative DNS server's answer to the end user's machine and may also cache the answer according to its time to live (TTL). The end user's machine then attempts to access the domain using the DNS record provided by the authoritative DNS server.